JP2013249917A - Fastening structure - Google Patents

Abstract

A fastening structure in which a plurality of structural members including a structural member made of magnesium alloy or aluminum alloy are fastened with a fastening member made of a metal having a higher potential than magnesium and aluminum. Prevent electrolytic corrosion.
A first structural member made of magnesium alloy or the like and a second structural member 20 are overlapped so that their mounting holes 11 and 21 are aligned, and a shaft portion 31a of a bolt 31 as a fastening member is placed in a first position. The mounting holes 11 and 21 are inserted from the side of the first structural member 10, and a nut 32 is screwed together from the side of the second structural member 20. A synthetic resin insulator 40 is interposed between the structural members 10 and 20 and the bolts 31 and nuts 32. The insulator 40 includes an integral sleeve 41, a flange 42, and a separate washer 43. Electrons are prevented from moving between the bolt 31 and the nut 32 and the structural members 10 and 20, and electrolytic corrosion can be prevented.
[Selection] Figure 1

Description

  The present invention relates to a fastening structure in which a plurality of overlapping structural members are fastened with fastening members.

Magnesium alloy casings are widely used as casings for personal computers and mobile phones.
This is used to reduce the weight of personal computers and mobile phones because magnesium is the lightest metal in practical use. Recently, in order to reduce the weight of automobiles, It has been studied that the structural member is made of a magnesium alloy.

By the way, when assembling a finished product from this type of structural member, a shaft inserted into the structural member such as a bolt, nut, rivet, fastener, anchor, pin, key, etc. in a state where a plurality of structural members overlap each other. It is often fastened by a fastening member having a portion and a head portion facing the outer surface of the structural member.
The fastening member is usually made of a metal that is more noble than magnesium such as iron, but when used for fastening a structural member made of magnesium alloy, the fastening member made of a noble metal and a structural member made of a base metal Will be in direct contact.
Furthermore, when rainwater or the like adheres to it and moisture intervenes, magnesium ionization is promoted, so that a structural member made of a base metal serves as an anode, a fastening member made of a noble metal serves as a cathode, and magnesium ions dissolve. A galvanic battery using the extracted water as an electrolyte is configured.
Therefore, electrolytic corrosion (galvanic corrosion) of the structural member serving as the anode occurs, which causes a decrease in strength such as the structural member being broken.

Since personal computers and mobile phones are rarely used in a harsh environment where a large amount of moisture adheres to the outer surface, the problem of electrolytic corrosion of the magnesium alloy casing has not become apparent.
However, when the use of magnesium alloys is widened and used in automobile bodies, etc., automobiles are used in harsh environments that cannot be compared with mobile phones, etc., so it is required to suppress the occurrence of such electrolytic corrosion as much as possible. .

Here, as in Patent Document 1, a structure in which a structural member made of a magnesium alloy is fastened with bolts and nuts made of an aluminum alloy has been devised.
If the bolt that is the fastening member is made of an aluminum alloy, the potential difference with magnesium can be reduced compared to the case where it is made of iron as in the prior art, so the occurrence of electrolytic corrosion can be reduced. For some reason, electrolytic corrosion cannot be completely prevented.
Even when the bolt surface is subjected to an oxide film treatment (alumite treatment: anodized is a registered trademark), electrolytic corrosion occurs if the film is peeled off due to friction or the like.

  The above problem is not only when the structural member is made of a magnesium alloy, but also when the structural member is made of a lightweight aluminum alloy among the practical metals, and the fastening member is made of a metal that is more precious than aluminum. Is also common.

JP 2008-32038 A

  Accordingly, a problem to be solved by the present invention is a fastening structure in which a plurality of structural members including a structural member made of magnesium alloy or aluminum alloy are fastened together with a fastening member made of metal that is more noble than magnesium and aluminum. The body is to prevent electrolytic corrosion of its structural members.

In order to solve the above-described problem, the fastening structure of the present invention includes a plurality of overlapping structural members including a specific structural member made of magnesium alloy or aluminum alloy having an attachment hole as an outermost layer, and the specific structural member A fastening member made of a metal having a potential higher than that of magnesium and aluminum having a shaft portion inserted into the mounting hole and a head portion opposed to the outer surface of the specific structural member, and a sleeve externally fitted to the shaft portion, And a synthetic resin insulator having a flange sandwiched between the head of the fastening member and the specific structural member.
The fastening member is not particularly limited as long as it has a head portion and a shaft portion, but is preferably a bolt / nut or rivet, fastener, anchor, pin, and key.

  It is preferable that the fastening structure further includes a synthetic resin sealing body that is laminated on at least the outer surface of the specific structural member so as to seal the head of the fastening member.

  Since an insulator made of synthetic resin is interposed between the specific structural member and the fastening member, the movement of electrons does not occur between the two and the electrolytic corrosion can be prevented.

  Sealing the head of the fastening member with a sealing body prevents moisture from entering between the fastening member and the specific structural member, thus preventing the generation of electrolyte due to moisture and further preventing electrolytic corrosion. can do.

Sectional drawing of the fastening structure of a 1st embodiment The perspective view of the insulator of the fastening structure of a 1st embodiment. Sectional drawing of the fastening structure of 2nd Embodiment Sectional drawing of the fastening structure of 3rd Embodiment Sectional drawing of the fastening structure of 4th Embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The fastening structure of the first embodiment shown in FIG. 1 is a structure in which the first structural member 10 and the second structural member 20 are overlapped and fastened by a bolt 31 and a nut 32 as the fastening member 30. For example, it is used as an automobile structure and its electrolytic corrosion is prevented.

The first structural member 10 as the specific structural member is made of a magnesium alloy or an aluminum alloy, and has an attachment hole 11 penetrating in the thickness direction.
The types of magnesium alloy and aluminum alloy are not particularly limited, and examples thereof include AZ91 (a magnesium alloy containing about 9% by weight of aluminum and about 1% by weight of zinc, with the balance being magnesium and inevitable impurities).
Although the thickness, dimension, shape, etc. are not particularly limited, the body of an automobile is mainly assumed.

The second structural member 20 has a mounting hole 21 penetrating in the thickness direction, and is superposed on the first structural member 10 so that the mounting hole 21 is aligned with the mounting hole 11 of the first structural member 10. I'm being fooled.
The material of the second structural member 20 is not particularly limited, and examples thereof include steel, synthetic resin, magnesium alloy, and aluminum alloy. Examples of steel include SPCC as cold rolled steel, and examples of synthetic resin include FRP (fiber reinforced plastic).
The thickness, size, shape, and the like are not particularly limited, but mainly an automobile frame, chassis, or the like is assumed.

The bolt 31 includes a shaft portion 31a and a head portion 31b formed integrally with the end portion of the shaft portion 31a, and the shaft portion 31a defines the mounting holes 11 and 21 of the first and second structural members 10 and 20. The head 31 b is inserted through the outer surface of the first structural member 10.
The nut 32 is screwed onto the tip of the shaft portion 31 a of the bolt 31 and faces the outer surface of the second structural member 20.
The bolt 31 and the nut 32 are made of a metal that is more noble than magnesium and aluminum. The material of the bolt 31 and the nut 32 is not particularly limited as long as the bolt 31 and the nut 32 are used.

An insulator 40 made of a hard synthetic resin is interposed between the bolt 31 and the nut 32 and the first and second structural members 10 and 20.
As shown in FIGS. 1 and 2, the insulator 40 includes a sleeve 41, a flange 42 formed integrally with the end of the sleeve 41, and a washer 43 separate from the sleeve 41.

The axial length of the cylindrical sleeve 41 is substantially equal to or slightly smaller than the sum of the thicknesses of the first and second structural members 10, 20, and this sleeve 41 is outside the entire length of the shaft portion 31 a of the bolt 31. The fitting holes 11 and 21 are inserted.
Further, the annular flange 42 is fitted on the base portion of the shaft portion 31 a of the bolt 31 and is sandwiched between the first structural member 10 and the head portion 31 b of the bolt 31 that face each other. Similarly, the annular washer 43 is fitted on the tip of the shaft portion 31 a of the bolt 31 and is sandwiched between the second structural member 20 and the nut 32 facing each other. As illustrated, the outer diameters of the flange 42 and the washer 43 are larger than the outer diameters of the head 31 b of the bolt 31 and the nut 32.
The material of the insulator 40 is not particularly limited as long as it is made of a hard synthetic resin and has electrical insulation, but examples thereof include acrylic, polyethylene, polypropylene, polyethylene terephthalate, polyacetal, polycarbonate, and MC nylon.

  The structure of the fastening structure of the first embodiment is as described above, and the insulator is between the first structural member 10 made of magnesium alloy or aluminum alloy and the bolt 31 made of a noble metal. Since the insulation is provided by the sleeve 41 and the flange 42, the movement of electrons between the first structural member 10 and the bolt 31 is prevented, and electrolytic corrosion of the first structural member 10 is prevented.

Similarly, since the second structural member 20 and the nut 32 are also insulated by the washer 43 of the insulator 40, electrolytic corrosion of the second structural member 20 is prevented.
Note that when the second structural member 20 is not made of a base metal such as a magnesium alloy or an aluminum alloy, the second structural member 20 is less susceptible to electrolytic corrosion. The washer 43 can be omitted as appropriate.
Similarly, when it is not necessary to insulate between the second structural member 20 and the shaft portion 31 a of the bolt 31, the axial length of the sleeve 41 of the insulator 40 is set to the mounting hole of the first structural member 10. It is possible to change the thickness of the first structural member 10 so as to be almost equal to the thickness of the first structural member 10.

In the fastening structure of the second embodiment shown in FIG. 3, the first structural member 10 as the specific structural member and the second structural member 20 are overlapped and fastened by a bolt 31 and a nut 32 as the fastening member 30. The insulator 40 is interposed between the bolt 31 and the nut 32 and the first and second structural members 10 and 20.
Hereinafter, detailed description of the same configuration as that of the first embodiment will be omitted.

In this embodiment, on the first structural member 10, the head portion 31 b of the bolt 31 is sealed by the sealing body 50 so as to be shielded from the outside air.
The sealing body 50 is formed by placing a fluid synthetic resin sealing material on the head portion 31b of the bolt 31 and curing the sealing material.
The material of the sealing body 50 is not particularly limited as long as it is made of a synthetic resin, and examples thereof include epoxy-based, urethane-based, acrylic-based, silicon-based, polysulfur-based, SBR-based, and butyl rubber-based caulking agents.
Similarly, on the second structural member 20, the nut 32 is sealed by the sealing body 50 so as to be shielded from the outside air.

Sealing the head portion 31b of the bolt 31 with the sealing body 50 prevents moisture from adhering to and intervening between the first structural member 10 and the bolt 31. Ionization can be suppressed and the occurrence of electrolytic corrosion can be further prevented.
Further, by sealing the nut 32 with the sealing body 50, it is possible to prevent moisture from entering from the gap between the nut 32 and the second structural member 20 into the first structural member 10 through the attachment hole 21. Similarly, ionization can be suppressed.
In addition, since the sealing body 50 that seals the nut 32 does not move electrons between the nut 32 and the second structural member 20 when the second structural member 20 is not made of a base metal. It can be omitted in consideration of cost and labor.
The shape between the members of the fastening portion is preferably smooth in order to prevent moisture from entering as much as possible, and the surface roughness is more preferably Rmax 5 μm.

The fastening structure of the third embodiment shown in FIG. 4 is a structure in which the first structural member 10 and the second structural member 20 are overlapped and fastened by a rivet 33 as a fastening member 30. Insulator 40 is interposed.
Hereinafter, detailed description of the same configuration as that of the first embodiment will be omitted.

The first structural member 10 as the specific structural member and the second structural member 20 are overlapped with their mounting holes 11 and 21 aligned, and a rivet 33 having a shaft portion 33a and a first head portion 33b. However, it is attached by inserting the shaft portion 33 a into the attachment holes 11 and 21 from the first structural member 10 side.
The rivet 33 has a second head portion 33c formed by crushing a tip portion of the shaft portion 33a protruding from the outer surface of the second structural member 20, whereby the first and second structural members 10, 20 are formed. Is concluded.
The material of the rivet 33 is not particularly limited as long as it is made of a metal that is more noble than the first structural member 10, but the same material as the bolt 31 can be exemplified. Further, when the first structural member 10 is made of a magnesium alloy, it may be made of a noble aluminum alloy.

Here, the diameter of the mounting hole 11 of the first structural member 10 is larger than the diameter of the mounting hole 21 of the second structural member 20, and the diameter of the mounting hole 21 is substantially equal to the diameter of the shaft portion 33 a of the rivet 33. The dimensions are equal or slightly larger.
The insulator 40 includes a cylindrical sleeve 41 and an annular flange 42 integrally formed at the end of the sleeve 41, and the axial length of the sleeve 41 is equal to the thickness of the first structural member 10. It is almost the same or slightly smaller.
The sleeve 41 is externally fitted to the shaft portion 33 a of the rivet 33, and the mounting hole of the first structural member 10 out of the mounting holes 11 and 21 of the first and second structural members 10 and 20 from the dimensional relationship described above. 11 is inserted only. The flange 42 is externally fitted to the root portion of the shaft portion 33 a of the rivet 33 and is sandwiched between the first head portion 33 b and the first structural member 10.
The insulator 40 is preliminarily fitted on the rivet 33 before the rivet 33 is attached to the first and second structural members.

In this embodiment, the washer of the insulator 40 is omitted in consideration of the cost and the like. However, if the second structural member 20 is made of a base metal, the washer is added to the second head. You may insulate by inserting | pinching between the part 33c and the 2nd structural member 20. FIG.
Similarly, the axial length of the sleeve 41 of the insulator 40 is increased, and accordingly, the diameter of the mounting hole 21 of the second structural member 20 is expanded so that the sleeve 41 can be inserted. The shaft portion 33a and the second structural member 20 may be insulated.
Further, similarly to the second embodiment, the first and second heads 33b and 33c of the rivet 33 may be sealed from a sealing body to block outside air.

In the fastening structure of the fourth embodiment shown in FIG. 5, the first structural member 10 and the second structural member 20 are overlapped and fastened by a self-piercing rivet 34 as a fastening member 30.
Hereinafter, detailed description of configurations similar to those of the first to third embodiments is omitted.

The first structural member 10 as the specific structural member in which the mounting hole 11 is formed and the second structural member 20 in which the mounting hole is not formed are overlapped, and a self having a hollow shaft portion 34a and a head portion 34b. The pierce rivet 34 has a shaft portion 34 a inserted into the mounting hole 11 from the first structural member 10 side.
Further, the tip portion of the shaft portion 34a of the self-piercing rivet 34 is appropriately driven into the plate surface of the second structural member 20 using a tool. The distal end of the hollow shaft portion 34a is deformed by spreading outward in the second structural member 20 as shown in the figure due to the load applied at the time of driving.
For this reason, the self-piercing rivet 34 is fixed to the second structural member 20, whereby the first and second structural members 10, 20 are fastened.

The insulator 40 includes a cylindrical sleeve 41 and an annular flange 42 formed integrally with the end portion of the sleeve 41. The sleeve 41 is fitted on the shaft portion 34a of the rivet 34 and has a first structure. The flange 42 is inserted only into the mounting hole 11 of the member 10, and is fitted on the root portion of the shaft portion 34 a of the rivet 34, and is sandwiched between the first head 34 b and the first structural member 10. Yes.
The insulator 40 is preliminarily fitted on the rivet 34 before the rivet 34 is attached to the first and second structural members.

  Furthermore, similarly to the second embodiment, the head 34b of the rivet 34 may be sealed from a sealing body to block outside air.

Regarding the fastening structures of the first, third, and fourth embodiments, the first structural member 10 obtained by electrodeposition coating on the AZ91 plate, and the second structural member 20 is subjected to baking coating on the SPCC plate. Prepared steel bolts chromated as bolts 31 and 1000 series aluminum alloy rivets as rivets 33 and self-piercing rivets 34, SST (salt spray test), and left for 96 hours after salt spray The presence or absence of corrosion was confirmed, but none of the corrosion occurred.
On the other hand, tests were performed under the same conditions except that no insulator was used. In all cases, corrosion occurred and the effect of the sealed body was confirmed.

  It should be considered that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications and variations within the scope and meaning equivalent to the terms of the claims.

For example, in the above-described embodiment, the rivet 33 including the bolt 31, the nut 32, and the self-piercing rivet 34 is illustrated as the fastening member 30. Is possible.
Moreover, although the aspect which two sheets overlap as a structural member was illustrated, it is not limited to this, Three or more sheets may be overlapped.
Even if the recess 42 is provided in the flange 42 of the insulator 40 and the bolt 31 and the heads 31b, 33b, 34b of the rivets 33, 34 are accommodated in the recess, the recess 50 is filled in the recess 50 from above. Good.

10 First structural member 11 Mounting hole 20 Second structural member 21 Mounting hole 30 Fastening member 31 Bolt 31a Shaft portion 31b Head portion 32 Nut 33 Rivet 33a Shaft portion 33b First head portion 33c Second head portion 34 Self Pierce rivet 34a Shaft 34b Head 40 Insulator 41 Sleeve 42 Flange 43 Washer 50 Sealing body

Claims (4)

A plurality of overlapping structural members including a specific structural member made of magnesium alloy or aluminum alloy with attachment holes formed as an outermost layer;
A fastening member made of a metal that is more noble than magnesium and aluminum, having a shaft portion inserted into the mounting hole of the specific structural member, and a head portion facing the outer surface of the specific structural member;
A fastening structure comprising: a sleeve fitted around the shaft portion; and a synthetic resin insulator having a flange sandwiched between a head of the fastening member and the specific structural member.   2. The fastening structure according to claim 1, further comprising a sealing body that is provided with a fluid synthetic resin material so as to block a head portion of the fastening member from outside air and is cured.   The fastening structure according to claim 1, wherein the fastening member is a bolt and a nut.   The fastening structure according to claim 1, wherein the fastening member is a rivet.

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